But veteran tactician Roux made an unusual attempt to temper the plaudits heading the youngster's way when he told Romanian broadcaster Dolce Sport: "I can assure you he is actually 23 or 24."

However, Santos was not about to indulge in speculation that he summarily dismissed, with the conspiracy grounded in Sanches' date of birth being officially registered late as a result of his parents separating.

"Sanches was born in Portugal, not just anywhere else, in Portugal. He is 18," he assured reporters ahead of Portugal's Euro 2016 semi-final against Wales in Lyon.

"I'm 61. There's no doubt about that. I was born 61 years ago and I'm 61. He was born 18 years ago and he's 18."

A potentially intriguing midfield battle between Sanches and Aaron Ramsey will not take place at the Stade de Lyon, with the Wales star banned due to collecting two bookings across the tournament's five matches.

Portugal's William Carvalho has suffered the same fate and Santos believes UEFA should consider a change of the rules under the expanded 24-team European Championship format.

"William isn't playing for us, and Aaron Ramsey isn't playing for Wales. It's a shame because I'd like every player to be eligible," he said.

"I'd say that, after the group stage, people shouldn't be punished for yellow cards. Red cards, yes. Yellows, no."

Wales boss Chris Coleman has labelled Portugal as favourites for the match, but Santos, who is full of admiration for a manager he met during their time working in Greece, does not subscribe to his assessment.

"Wales have had an incredible run," he added. "They've been playing incredibly.

"They finished first in a very tight group. They beat one of the major teams in Belgium, ranked number one [two] in the world. They beat them 3-1.

"I deeply respect Chris Coleman. I've spoken to him once or twice in Greece, a great manager, but that's his mind game.

"I don't think he's telling his team that Portugal are favourites. I think this is a game between two huge teams and that we will win, but that's another matter."